1. Field of the Invention
The present invention relates generally to position sensors and more particularly to a non-contact position sensor.
2. Description of the Prior Art
There is an increasing need for small, reliable, low cost electro mechanical integrated devices that can be used in system type applications, for example systems for measuring throttle angle in a vehicle, or shaft angle of a tool, displacement of a linear actuator or solenoid, monitoring a condition such as the physical amount of wear on a component so that replacement can be made in a planned orderly way rather than after a failure due to excessive wear. These applications are only a few examples of a need that could possibly be met by such an integrated position sensing device.
Various non-contact position sensor arrangements or magnetic potentiometers using Hall effect devices have been proposed in the past. In one such arrangement a Hall effect device is fixed at a location and permanent magnets are mounted so as to be spaced from the Hall element and to vary the magnetic flux density at the Hall element as the magnets are rotated. Various geometries for the shape of the magnets, the spacing of the magnets and the inclination of the magnets have been proposed. These approaches tend to require relatively large and strong magnets that have been carefully matched and in addition these approaches require precise construction to achieve the proper relationships when the magnets are rotated. In addition temperature compensation techniques are needed.
In another proposed position sensor uses a closed circuit including magnets are yokes. Magnetic leakage flux emanates from the inside surfaces of the yokes and a magnetic sensor is moved along the inside surfaces of the yokes to detect position. The movement of the magnetic sensor results in a complex arrangement.
Thus a need exists for a simple, reliable low cost non contact magnetic position sensor.